PURE EVIL:Horrific security video shows the deadly sequence yesterday of a madman spraying his elderly victim in an elevator with accelerant, and about to set her alight.

A Brooklyn woman was horrifically burned to death in her apartment-building elevator yesterday when a maniac guy-pal sprayed her with flammable liquid and set her alight with a Molotov cocktail, cops said.

“She was screaming at the top of her lungs,” said a resident of the Prospect Heights building who heard the sounds of the struggle at around 4:15 p.m.

The 64-year-old victim, who sources identified as Dolores Gillespie, was returning from grocery shopping when the elevator stopped on the fifth floor of the building at 203 Underhill Ave.